NU National Union 7N7 Loktal AT1000 TESTED Vacuum Tube greyglass T1 rare support rods triple mica early military dual triode (like 6SN7) 1941-1946

This listing is for one (1) National Union-made 7N7 dual triode (like 6SN7) Loktal vacuum tube in the straight-walled glass tube shape. It has a Metal Loktal base, grey or black glass from a coating used as an RF shield in early tubes, black round plate, and top square getter.

We believe 7N7 tubes were made only by Sylvania and NU. They have been given "type codes" by Sound by Doc as follows: T1 (194?) NU round plate, grey glass, tall bottle, support rods. T2 (1944-5) tall glass, foil getter, inward-facing 2-hole carbonized black T plates, 4 spider legs holding top mica. T3 (194?) Military, identical to T2 but square getter. T4 (1947-9) short bottle, foil getter, carbonized black T plates, no spider legs on upper mica. 1949 versions have points on the bottom racetrack mica. T5 (1950) identical to T4 but shiny black plates. T6 (1950-1952) tall bottle, foil getter, grey T-plates. T7 (1951) short bottle. T8 (1951-2) tall bottle, shiny black plates, racetrack upper and lower micas with no points. T9 (1952-3) BAD BOYS! Grey short glass, three-hole inward-facing T-plates! Same plates Sylvania was putting into 6SN7 during the same years. T10 (1954-8) clear glass, angled black T-plates. Some T10 are mislabeled as Mullard 7F7!!! T11 (1959-1960s) same as T10 but with halo getter and stop-sign missing from top.

Your tube has been fully tested on a computer-regulated, USA-made Amplitrex AT1000 on Fixed Bias setting with used good results. It has also passed shorts and gas tests. The tube might have mechanical wear or have the label rubbed off - these are very old! Tubes that test like new (tNOS) are available in a separate listing. Every tNOS or Used Good tube you receive from Sound By Doc is guaranteed against failure for 60 days after purchase, an industry extreme!

These photos are not stock photos. You are looking at the actual tube you will receive. If a box or boxes are in the photos, you will get them. If test results appear in the photos, look close, because those are the test results of the tube you will receive! SKU LOK-7N7T1-rpu. Please note that matching is nearly always possible for us from stock that is inventoried but not yet listed. If you need a matched pair or quad etc., please use the make-an-offer feature through Reverb. Matching requires an extra burst of effort, so please add $5 per tube to your offer for 10% matching and $10 per tube for 4% matching. [Matching is based on plate current for power tubes, voltage drop for rectifiers, and GM for all other tubes. If you also require the label or internals to match, please specify that in your offer.]